What were the questions that were asked in the IIT Delhi M.Tech interview for Computer Science and Engineering?

My friend recently gave his interview for the MTech program at IIT Delhi and he told me that only 2 questions were asked him.

• What is a tree? - To this, my friend gave a general answer that did not satisfy them, after which they asked him to state an additional property of the tree. Right after this, they tricked him by asking him to prove the 2nd property based on the first. Although he tried, he was unable to give the final solution.
• Next, they chose a number between 0 to infinity and asked him to guess their number exactly using the minimum number of queries. My friend could answer this one better than the first one although the panelists weren’t completely satisfied with this one too.

His interview lasted the longest although he was asked only 2 questions. Some conclusions drawn from his experience and tips to follow to prepare for the same are

• Study the proofs from Discrete Math and Data Structure and Algorithms. 
• Be well-versed with all major definitions and prepare some good examples to support your definition. 
• Explain the questions asked in detail and not in short

Hope you got an idea of the type of questions asked in the MTech CSE interview.